<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0.1 Transitional//EN"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> <title>Boost.MultiIndex Documentation - Key extraction reference</title> <link rel="stylesheet" href="../style.css" type="text/css"> <link rel="start" href="../index.html"> <link rel="prev" href="rnd_indices.html"> <link rel="up" href="index.html"> <link rel="next" href="../compiler_specifics.html"> </head> <body> <h1><img src="../../../../boost.png" alt="boost.png (6897 bytes)" align= "middle" width="277" height="86">Boost.MultiIndex Key extraction reference</h1> <div class="prev_link"><a href="rnd_indices.html"><img src="../prev.gif" alt="random access indices" border="0"><br> Random access indices </a></div> <div class="up_link"><a href="index.html"><img src="../up.gif" alt="Boost.MultiIndex reference" border="0"><br> Boost.MultiIndex reference </a></div> <div class="next_link"><a href="../compiler_specifics.html"><img src="../next.gif" alt="compiler specifics" border="0"><br> Compiler specifics </a></div><br clear="all" style="clear: all;"> <hr> <h2>Contents</h2> <ul> <li><a href="#key_extractors">Key Extractors</a> <ul> <li><a href="#chained_pointers">Chained pointers</a></li> </ul> </li> <li><a href="#synopsis">Header <code>"boost/multi_index/key_extractors.hpp"</code> synopsis</a> </li> <li><a href="#identity_synopsis">Header <code>"boost/multi_index/identity.hpp"</code> synopsis</a> <ul> <li><a href="#identity">Class template <code>identity</code></a></li> </ul> </li> <li><a href="#member_synopsis">Header <code>"boost/multi_index/member.hpp"</code> synopsis</a> <ul> <li><a href="#member">Class template <code>member</code></a></li> <li><a href="#member_offset">Class template <code>member_offset</code></a></li> <li><a href="#boost_multi_index_member">Macro <code>BOOST_MULTI_INDEX_MEMBER</code></a></li> </ul> </li> <li><a href="#mem_fun_synopsis">Header <code>"boost/multi_index/mem_fun.hpp"</code> synopsis</a> <ul> <li><a href="#const_mem_fun">Class template <code>const_mem_fun</code></a></li> <li><a href="#mem_fun">Class template <code>mem_fun</code></a></li> <li><a href="#const_mem_fun_explicit">Class template <code>const_mem_fun_explicit</code></a></li> <li><a href="#mem_fun_explicit">Class template <code>mem_fun_explicit</code></a></li> <li><a href="#boost_multi_index_const_mem_fun">Macro <code>BOOST_MULTI_INDEX_CONST_MEM_FUN</code></a></li> <li><a href="#boost_multi_index_mem_fun">Macro <code>BOOST_MULTI_INDEX_MEM_FUN</code></a></li> </ul> </li> <li><a href="#global_fun_synopsis">Header <code>"boost/multi_index/global_fun.hpp"</code> synopsis</a> <ul> <li><a href="#global_fun">Class template <code>global_fun</code></a></li> </ul> </li> <li><a href="#composite_key_synopsis">Header <code>"boost/multi_index/composite_key.hpp"</code> synopsis</a> <ul> <li><a href="#composite_key">Class template <code>composite_key</code></a></li> <li><a href="#composite_key_result">Class template <code>composite_key_result</code></a></li> <li><a href="#ckey_result_equality">Equality</a> <ul> <li><a href="#composite_key_equal_to">Class template <code>composite_key_equal_to</code></a></li> <li><a href="#composite_key_result_equal_to">Class template <code>composite_key_result_equal_to</code></a></li> <li><a href="#equal_to_composite_key_result">Specialization of <code>std::equal_to</code> for <code>composite_key</code> results</a></li> </ul> </li> <li><a href="#ckey_result_comparison">Comparison</a> <ul> <li><a href="#composite_key_compare">Class template <code>composite_key_compare</code></a></li> <li><a href="#composite_key_result_less">Class template <code>composite_key_result_less</code></a></li> <li><a href="#composite_key_result_greater">Class template <code>composite_key_result_greater</code></a></li> <li><a href="#less_composite_key_result">Specialization of <code>std::less</code> for <code>composite_key</code> results</a></li> <li><a href="#greater_composite_key_result">Specialization of <code>std::greater</code> for <code>composite_key</code> results</a></li> </ul> </li> <li><a href="#ckey_result_hashing">Hashing</a> <ul> <li><a href="#composite_key_hash">Class template <code>composite_key_hash</code></a></li> <li><a href="#composite_key_result_hash">Class template <code>composite_key_result_hash</code></a></li> <li><a href="#hash_composite_key_result">Specialization of <code>boost::hash</code> for <code>composite_key</code> results</a></li> </ul> </li> <li><a href="#ckey_result_semantics">Semantics of <code>composite_key_result</code></a></li> </ul> </li> </ul> <h2><a name="key_extractors">Key Extractors</a></h2> <p> Key extraction classes are used by <a href="indices.html#key_based_indices">key-based indices</a> to obtain the indexing keys from the elements of a <code>multi_index_container</code>. An <a href="http://www.sgi.com/tech/stl/Assignable.html"><code>Assignable</code></a> class <code>KeyFromValue</code> is said to be a key extractor from a type <code>Type</code> if <ol> <li>the type <code>KeyFromValue::result_type</code> is defined,</li> <li><code>k1(ca)</code> is defined and returns a value convertible to <code>const KeyFromValue::result_type&</code>,</li> <li>if <code>k2</code> is a copy of <code>k1</code>, <code>k1(ca)</code> is the same value as <code>k2(ca)</code>,</li> </ol> for every <code>k1</code>, <code>k2</code> of type <code>const KeyFromValue</code>, and <code>ca</code> of type <code>const Type&</code>. </p> <p> Additionally, <code>KeyFromValue</code> is a <i>read/write</i> key extractor if the following extra conditions are met: <ol> <li><code>k1(a)</code> is defined and returns a value convertible to <code>KeyFromValue::result_type&</code>,</li> <li><code>const_cast<const KeyFromValue::result_type&>(k1(a))</code> is the same value as <code>k1(const_cast<const Type&>(a))</code>,</li> </ol> for every <code>k1</code> of type <code>const KeyFromValue</code> and <code>a</code> of type <code>Type&</code>. </p> <p> Boost.MultiIndex provides six general-purpose key extractors: <ul> <li><a href="#identity"><code>identity</code></a>,</li> <li><a href="#member"><code>member</code></a>,</li> <li><a href="#const_mem_fun"><code>const_mem_fun</code></a>,</li> <li><a href="#mem_fun"><code>mem_fun</code></a>,</li> <li><a href="#global_fun"><code>global_fun</code></a> and</li> <li><a href="#composite_key"><code>composite_key</code></a>,</li> </ul> plus replacements for some of them: <ul> <li><a href="#member_offset"><code>member_offset</code></a>,</li> <li><a href="#const_mem_fun_explicit"><code>const_mem_fun_explicit</code></a> and</li> <li><a href="#mem_fun_explicit"><code>mem_fun_explicit</code></a>,</li> </ul> that workaround some deficiencies in the support for non-type template parameters by certain compilers. </p> <h3><a name="chained_pointers">Chained pointers</a></h3> <p> The key extractors provided by Boost.MultiIndex are templatized according to the type <code>Type</code> and serve to extract keys not only from objects of type <code>Type</code>, but also from reference wrappers provided by <a href="../../../../doc/html/ref.html">Boost.Ref</a> and from <i>chained pointers</i> to <code>Type</code> (or to reference wrappers of <code>Type</code>): a chained pointer is any type <code>P</code> such that, for an object <code>p</code> of type <code>const P</code> <ul> <li><code>*p</code> yields an object of type <code>Type&</code> or <code>boost::reference_wrapper<Type></code>, OR</li> <li><code>*p</code> yields a chained pointer to <code>Type</code>,</li> </ul> that is, chained pointers are arbitrary compositions of pointer-like objects ultimately dereferencing to values of <code>Type&</code> or <code>boost::reference_wrapper<Type></code>. <p> <h2><a name="synopsis">Header <a href="../../../../boost/multi_index/key_extractors.hpp"> <code>"boost/multi_index/key_extractors.hpp"</code></a> synopsis</a> </h2> <blockquote><pre> <span class=preprocessor>#include</span> <span class=special><</span><span class=identifier>boost</span><span class=special>/</span><span class=identifier>multi_index</span><span class=special>/</span><span class=identifier>identity</span><span class=special>.</span><span class=identifier>hpp</span><span class=special>></span> <span class=preprocessor>#include</span> <span class=special><</span><span class=identifier>boost</span><span class=special>/</span><span class=identifier>multi_index</span><span class=special>/</span><span class=identifier>member</span><span class=special>.</span><span class=identifier>hpp</span><span class=special>></span> <span class=preprocessor>#include</span> <span class=special><</span><span class=identifier>boost</span><span class=special>/</span><span class=identifier>multi_index</span><span class=special>/</span><span class=identifier>mem_fun</span><span class=special>.</span><span class=identifier>hpp</span><span class=special>></span> <span class=preprocessor>#include</span> <span class=special><</span><span class=identifier>boost</span><span class=special>/</span><span class=identifier>multi_index</span><span class=special>/</span><span class=identifier>global_fun</span><span class=special>.</span><span class=identifier>hpp</span><span class=special>></span> <span class=preprocessor>#include</span> <span class=special><</span><span class=identifier>boost</span><span class=special>/</span><span class=identifier>multi_index</span><span class=special>/</span><span class=identifier>composite_key</span><span class=special>.</span><span class=identifier>hpp</span><span class=special>></span> </pre></blockquote> <p> This header includes all the key extractors provided by Boost.MultiIndex. </p> <h2> <a name="identity_synopsis">Header <a href="../../../../boost/multi_index/identity.hpp"> <code>"boost/multi_index/identity.hpp"</code></a> synopsis</a></h2> <blockquote><pre> <span class=keyword>namespace</span> <span class=identifier>boost</span><span class=special>{</span> <span class=keyword>namespace</span> <span class=identifier>multi_index</span><span class=special>{</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>T</span><span class=special>></span> <span class=keyword>struct</span> <span class=identifier>identity</span><span class=special>;</span> <span class=special>}</span> <span class=comment>// namespace boost::multi_index</span> <span class=special>}</span> <span class=comment>// namespace boost</span> </pre></blockquote> <h3><a name="identity">Class template <code>identity</code></a></h3> <p> <code>identity</code> is a <a href="#key_extractors"><code>Key Extractor</code></a> that acts as a do-nothing identity functor. </p> <blockquote><pre> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>Type</span><span class=special>></span> <span class=keyword>struct</span> <span class=identifier>identity</span> <span class=special>{</span> <span class=keyword>typedef</span> <span class=identifier>Type</span> <span class=identifier>result_type</span><span class=special>;</span> <span class=comment>// only provided if const ChainedPtr& is not convertible to const Type&</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>ChainedPtr</span><span class=special>></span> <span class=identifier>Type</span><span class=special>&</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>ChainedPtr</span><span class=special>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=keyword>const</span> <span class=identifier>Type</span><span class=special>&</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>Type</span><span class=special>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=identifier>Type</span><span class=special>&</span> <span class=keyword>operator</span><span class=special>()(</span><span class=identifier>Type</span><span class=special>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=comment>// only provided if Type is non-const // only provided if Type is non-const</span> <span class=keyword>const</span> <span class=identifier>Type</span><span class=special>&</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special><</span><span class=keyword>const</span> <span class=identifier>Type</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=comment>// only provided if Type is const</span> <span class=identifier>Type</span><span class=special>&</span> <span class=keyword>operator</span><span class=special>()(</span> <span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>remove_const</span><span class=special><</span><span class=identifier>Type</span><span class=special>>::</span><span class=identifier>type</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=identifier>Type</span><span class=special>&</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special><</span><span class=identifier>Type</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=special>};</span> </pre></blockquote> <p> <code>identity<Type></code> is a model of: <ul> <li>read/write <a href="#key_extractors"><code>Key Extractor</code></a> from <code>Type</code>,</li> <li><a href="#key_extractors"><code>Key Extractor</code></a> from <code>reference_wrapper<const Type></code>,</li> <li>read/write <a href="#key_extractors"><code>Key Extractor</code></a> from <code>reference_wrapper<Type></code>,</li> <li><a href="#key_extractors"><code>Key Extractor</code></a> from any <a href="#chained_pointers">chained pointer</a> to <code>const Type</code>,</li> <li>read/write <a href="#key_extractors"><code>Key Extractor</code></a> from any <a href="#chained_pointers">chained pointer</a> to <code>Type</code>.</li> </ul> </p> <h4><code>identity</code> members</h4> <code>template<typename ChainedPtr> Type& operator()(const ChainedPtr& x)const;</code> <blockquote> <b>Requires:</b> <code>ChainedPtr</code> is a <a href="#chained_pointers">chained pointer</a> type to <code>Type</code>.<br> <b>Returns:</b> a reference to the object chained-pointed to by <code>x</code>. </blockquote> <code>const Type& operator()(const Type& x)const;</code> <blockquote> <b>Returns:</b> <code>x</code>. </blockquote> <code>Type& operator()(Type& x)const;</code> <blockquote> <b>Returns:</b> <code>x</code>. </blockquote> <code>const Type& operator()(const reference_wrapper<const Type>& x)const;</code> <blockquote> <b>Returns:</b> <code>x.get()</code>. </blockquote> <code>Type& operator()(const reference_wrapper<typename remove_const<Type>::type>& x)const;</code> <blockquote> <b>Returns:</b> <code>x.get()</code>. </blockquote> <code>Type& operator()(const reference_wrapper<Type>& x)const;</code> <blockquote> <b>Returns:</b> <code>x.get()</code>. </blockquote> <h2> <a name="member_synopsis">Header <a href="../../../../boost/multi_index/member.hpp"> <code>"boost/multi_index/member.hpp"</code></a> synopsis</a></h2> <blockquote><pre> <span class=keyword>namespace</span> <span class=identifier>boost</span><span class=special>{</span> <span class=keyword>namespace</span> <span class=identifier>multi_index</span><span class=special>{</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>class</span> <span class=identifier>Class</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Type</span><span class=special>,</span><span class=identifier>Type</span> <span class=identifier>Class</span><span class=special>::*</span><span class=identifier>PtrToMember</span><span class=special>></span> <span class=keyword>struct</span> <span class=identifier>member</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>class</span> <span class=identifier>Class</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Type</span><span class=special>,</span><span class=identifier>std</span><span class=special>::</span><span class=identifier>size_t</span> <span class=identifier>OffsetOfMember</span><span class=special>></span> <span class=keyword>struct</span> <span class=identifier>member_offset</span><span class=special>;</span> <span class=preprocessor>#define</span> <span class=identifier>BOOST_MULTI_INDEX_MEMBER</span><span class=special>(</span><span class=identifier>Class</span><span class=special>,</span><span class=identifier>Type</span><span class=special>,</span><span class=identifier>MemberName</span><span class=special>)</span> <b>implementation defined</b> <span class=special>}</span> <span class=comment>// namespace boost::multi_index</span> <span class=special>}</span> <span class=comment>// namespace boost</span> </pre></blockquote> <h3><a name="member">Class template <code>member</code></a></h3> <p> <code>member</code> is a <a href="#key_extractors"><code>Key Extractor</code></a> aimed at accessing a given member of a class. </p> <blockquote><pre> <span class=keyword>template</span><span class=special><</span><span class=keyword>class</span> <span class=identifier>Class</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Type</span><span class=special>,</span><span class=identifier>Type</span> <span class=identifier>Class</span><span class=special>::*</span><span class=identifier>PtrToMember</span><span class=special>></span> <span class=keyword>struct</span> <span class=identifier>member</span> <span class=special>{</span> <span class=keyword>typedef</span> <span class=identifier>Type</span> <span class=identifier>result_type</span><span class=special>;</span> <span class=comment>// only provided if const ChainedPtr& is not convertible to const Class&</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>ChainedPtr</span><span class=special>></span> <span class=identifier>Type</span><span class=special>&</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>ChainedPtr</span><span class=special>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=keyword>const</span> <span class=identifier>Type</span><span class=special>&</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>Class</span><span class=special>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=identifier>Type</span><span class=special>&</span> <span class=keyword>operator</span><span class=special>()(</span><span class=identifier>Class</span><span class=special>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=comment>// only provided if Type is non-const</span> <span class=keyword>const</span> <span class=identifier>Type</span><span class=special>&</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special><</span><span class=keyword>const</span> <span class=identifier>Class</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=identifier>Type</span><span class=special>&</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special><</span><span class=identifier>Class</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=special>};</span> </pre></blockquote> <p> The <code>PtrToMember</code> template argument specifies the particular <code>Type Class::*</code> pointer to the member to be extracted. <code>member<Class,Type,PtrToMember></code> is a model of: <ul> <li>read/write <a href="#key_extractors"><code>Key Extractor</code></a> from <code>Class</code>,</li> <li><a href="#key_extractors"><code>Key Extractor</code></a> from <code>reference_wrapper<const Class></code>,</li> <li>read/write <a href="#key_extractors"><code>Key Extractor</code></a> from <code>reference_wrapper<Class></code>,</li> <li><a href="#key_extractors"><code>Key Extractor</code></a> from any <a href="#chained_pointers">chained pointer</a> to <code>const Class</code>,</li> <li>read/write <a href="#key_extractors"><code>Key Extractor</code></a> from any <a href="#chained_pointers">chained pointer</a> to <code>Class</code>.</li> </ul> </p> <h4><code>member</code> members</h4> <code>template<typename ChainedPtr> Type& operator()(const ChainedPtr& x)const;</code> <blockquote> <b>Requires:</b> <code>ChainedPtr</code> is a <a href="#chained_pointers">chained pointer</a> type to <code>Type</code>.<br> <b>Returns:</b> a reference to the object chained-pointed to by <code>x</code>. </blockquote> <code>const Type& operator()(const Class& x)const;</code> <blockquote> <b>Returns:</b> <code>x.*PtrToMember</code>. </blockquote> <code>Type& operator()(Class& x)const;</code> <blockquote> <b>Returns:</b> <code>x.*PtrToMember</code>. </blockquote> <code>const Type& operator()(const reference_wrapper<const Class>& x)const;</code> <blockquote> <b>Returns:</b> <code>x.get().*PtrToMember</code>. </blockquote> <code>Type& operator()(const reference_wrapper<Class>& x)const;</code> <blockquote> <b>Returns:</b> <code>x.get().*PtrToMember</code>. </blockquote> <h3><a name="member_offset">Class template <code>member_offset</code></a></h3> <p> Some compilers do not properly support pointers to members as non-type template arguments. The following have been confirmed to have bugs in this respect: <ul> <li>MSVC++ 6.0 (see <a href="http://support.microsoft.com/default.aspx?scid=kb;EN-US;249045">Microsoft Knowledge Base article #249045</a>),</li> <li>MSVC++ 7.0 (not officially confirmed by Microsoft),</li> <li>Intel C++ 7.0/7.1 for Windows (support issue #207321),</li> <li>VisualAge 6.0 for AIX (internal defect #288539.)</li> </ul> In this situation, <code>member_offset</code> provides an alternative to <a href="#member"><code>member</code></a> accepting offsets instead of pointers to members. Please note that the use of <code>offsetof</code> on non-POD types is forbidden by the standard; luckily enough, most compilers accept it nevertheless, so <code>member_offset</code> serves as a workaround for most practical purposes. </p> <blockquote><pre> <span class=keyword>template</span><span class=special><</span><span class=keyword>class</span> <span class=identifier>Class</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Type</span><span class=special>,</span><span class=identifier>std</span><span class=special>::</span><span class=identifier>size_t</span> <span class=identifier>OffsetOfMember</span><span class=special>></span> <span class=keyword>struct</span> <span class=identifier>member_offset</span> <span class=special>{</span> <span class=keyword>typedef</span> <span class=identifier>Type</span> <span class=identifier>result_type</span><span class=special>;</span> <span class=comment>// only provided if const ChainedPtr& is not convertible to const Class&</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>ChainedPtr</span><span class=special>></span> <span class=identifier>Type</span><span class=special>&</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>ChainedPtr</span><span class=special>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=keyword>const</span> <span class=identifier>Type</span><span class=special>&</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>Class</span><span class=special>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=identifier>Type</span><span class=special>&</span> <span class=keyword>operator</span><span class=special>()(</span><span class=identifier>Class</span><span class=special>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=comment>// only provided if Type is non-const</span> <span class=keyword>const</span> <span class=identifier>Type</span><span class=special>&</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special><</span><span class=keyword>const</span> <span class=identifier>Class</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=identifier>Type</span><span class=special>&</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special><</span><span class=identifier>Class</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=special>};</span> </pre></blockquote> <p>As an example of use, given the class</p> <blockquote><pre> <span class=keyword>class</span> <span class=identifier>A</span> <span class=special>{</span> <span class=keyword>int</span> <span class=identifier>x</span><span class=special>;</span> <span class=special>}</span> </pre></blockquote> <p> the instantiation <code>member<A,int,&A::x></code> can be simulated then as <code>member_offset<A,int,offsetof(A,x)></code>. </p> <h3><a name="boost_multi_index_member">Macro <code>BOOST_MULTI_INDEX_MEMBER</code></a></h3> <blockquote><pre> <span class=identifier>BOOST_MULTI_INDEX_MEMBER</span><span class=special>(</span><span class=identifier>Class</span><span class=special>,</span><span class=identifier>Type</span><span class=special>,</span><span class=identifier>MemberName</span><span class=special>)</span> </pre></blockquote> <p> This macro is provided as an aid for using <code>member</code> and <code>member_offset</code> when writing cross-platform code. In the usual cases, it expands to </p> <blockquote><pre> <span class=special>::</span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>member</span><span class=special><</span><span class=identifier>Class</span><span class=special>,</span><span class=identifier>Type</span><span class=special>,&</span><span class=identifier>Class</span><span class=special>::</span><span class=identifier>MemberName</span><span class=special>></span> </pre></blockquote> <p> but it resolves to </p> <blockquote><pre> <span class=special>::</span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>member_offset</span><span class=special><</span><span class=identifier>Class</span><span class=special>,</span><span class=identifier>Type</span><span class=special>,</span><span class=identifier>offsetof</span><span class=special>(</span><span class=identifier>Class</span><span class=special>,</span><span class=identifier>MemberName</span><span class=special>)></span> </pre></blockquote> <p> if the <a href="../../../../libs/config/config.htm">Boost Configuration Library</a> defect macro <code>BOOST_NO_POINTER_TO_MEMBER_TEMPLATE_PARAMETERS</code> is defined. </p> <h2> <a name="mem_fun_synopsis">Header <a href="../../../../boost/multi_index/mem_fun.hpp"> <code>"boost/multi_index/mem_fun.hpp"</code></a> synopsis</a></h2> <blockquote><pre> <span class=keyword>namespace</span> <span class=identifier>boost</span><span class=special>{</span> <span class=keyword>namespace</span> <span class=identifier>multi_index</span><span class=special>{</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>class</span> <span class=identifier>Class</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Type</span><span class=special>,</span><span class=identifier>Type</span> <span class=special>(</span><span class=identifier>Class</span><span class=special>::*</span><span class=identifier>PtrToMemberFunction</span><span class=special>)()</span><span class=keyword>const</span><span class=special>></span> <span class=keyword>struct</span> <span class=identifier>const_mem_fun</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>class</span> <span class=identifier>Class</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Type</span><span class=special>,</span><span class=identifier>Type</span> <span class=special>(</span><span class=identifier>Class</span><span class=special>::*</span><span class=identifier>PtrToMemberFunction</span><span class=special>)()></span> <span class=keyword>struct</span> <span class=identifier>mem_fun</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span> <span class=keyword>class</span> <span class=identifier>Class</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Type</span><span class=special>,</span> <span class=keyword>typename</span> <span class=identifier>PtrToMemberFunctionType</span><span class=special>,</span><span class=identifier>PtrToMemberFunctionType</span> <span class=identifier>PtrToMemberFunction</span> <span class=special>></span> <span class=keyword>struct</span> <span class=identifier>const_mem_fun_explicit</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span> <span class=keyword>class</span> <span class=identifier>Class</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Type</span><span class=special>,</span> <span class=keyword>typename</span> <span class=identifier>PtrToMemberFunctionType</span><span class=special>,</span><span class=identifier>PtrToMemberFunctionType</span> <span class=identifier>PtrToMemberFunction</span> <span class=special>></span> <span class=keyword>struct</span> <span class=identifier>mem_fun_explicit</span><span class=special>;</span> <span class=preprocessor>#define</span> <span class=identifier>BOOST_MULTI_INDEX_CONST_MEM_FUN</span><span class=special>(</span><span class=identifier>Class</span><span class=special>,</span><span class=identifier>Type</span><span class=special>,</span><span class=identifier>MemberFunName</span><span class=special>)</span> <span class=special>\</span> <b>implementation defined</b> <span class=preprocessor>#define</span> <span class=identifier>BOOST_MULTI_INDEX_MEM_FUN</span><span class=special>(</span><span class=identifier>Class</span><span class=special>,</span><span class=identifier>Type</span><span class=special>,</span><span class=identifier>MemberFunName</span><span class=special>)</span> <span class=special>\</span> <b>implementation defined</b> <span class=special>}</span> <span class=comment>// namespace boost::multi_index</span> <span class=special>}</span> <span class=comment>// namespace boost</span> </pre></blockquote> <h3><a name="const_mem_fun">Class template <code>const_mem_fun</code></a></h3> <p> <code>const_mem_fun</code> is a <a href="#key_extractors"><code>Key Extractor</code></a> returning as key the result of invoking a given constant member function of a class. </p> <blockquote><pre> <span class=keyword>template</span><span class=special><</span><span class=keyword>class</span> <span class=identifier>Class</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Type</span><span class=special>,</span><span class=identifier>Type</span> <span class=special>(</span><span class=identifier>Class</span><span class=special>::*</span><span class=identifier>PtrToMemberFunction</span><span class=special>)()</span><span class=keyword>const</span><span class=special>></span> <span class=keyword>struct</span> <span class=identifier>const_mem_fun</span> <span class=special>{</span> <span class=keyword>typedef</span> <span class=keyword>typename</span> <span class=identifier>remove_reference</span><span class=special><</span><span class=identifier>Type</span><span class=special>>::</span><span class=identifier>type</span> <span class=identifier>result_type</span><span class=special>;</span> <span class=comment>// only provided if const ChainedPtr& is not convertible to const Class&</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>ChainedPtr</span><span class=special>></span> <span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>ChainedPtr</span><span class=special>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>Class</span><span class=special>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special><</span><span class=keyword>const</span> <span class=identifier>Class</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special><</span><span class=identifier>Class</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=special>};</span> </pre></blockquote> <p> The <code>PtrToMemberFunction</code> template argument specifies the particular <code>Type (Class::*PtrToMemberFunction)()const</code> pointer to the the constant member function used in the extraction. <code>const_mem_fun<Class,Type,PtrToMemberFunction></code> is a model of: <ul> <li><a href="#key_extractors"><code>Key Extractor</code></a> from <code>Class</code>,</li> <li><a href="#key_extractors"><code>Key Extractor</code></a> from <code>reference_wrapper<const Class></code>,</li> <li><a href="#key_extractors"><code>Key Extractor</code></a> from <code>reference_wrapper<Class></code>,</li> <li><a href="#key_extractors"><code>Key Extractor</code></a> from any <a href="#chained_pointers">chained pointer</a> to <code>const Class</code>,</li> <li><a href="#key_extractors"><code>Key Extractor</code></a> from any <a href="#chained_pointers">chained pointer</a> to <code>Class</code>.</li> </ul> </p> <h4><code>const_mem_fun</code> members</h4> <code>template<typename ChainedPtr> Type operator()(const ChainedPtr& x)const;</code> <blockquote> <b>Requires:</b> <code>ChainedPtr</code> is a <a href="#chained_pointers">chained pointer</a> type to <code>Type</code>.<br> <b>Returns:</b> <code>(y.*PtrToMemberFunction)()</code>, where <code>y</code> is the object chained-pointed to by <code>x</code>. </blockquote> <code>Type operator()(const Class& x)const;</code> <blockquote> <b>Returns:</b> <code>(x.*PtrToMemberFunction)()</code>. </blockquote> <code>Type operator()(const reference_wrapper<const Class>& x)const;</code> <blockquote> <b>Returns:</b> <code>(x.get().*PtrToMemberFunction)()</code>. </blockquote> <code>Type operator()(const reference_wrapper<Class>& x)const;</code> <blockquote> <b>Returns:</b> <code>(x.get().*PtrToMemberFunction)()</code>. </blockquote> <h3><a name="mem_fun">Class template <code>mem_fun</code></a></h3> <p> <code>mem_fun</code> is a <a href="#key_extractors"><code>Key Extractor</code></a> returning as key the result of invoking a given member function of a class. </p> <blockquote><pre> <span class=keyword>template</span><span class=special><</span><span class=keyword>class</span> <span class=identifier>Class</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Type</span><span class=special>,</span><span class=identifier>Type</span> <span class=special>(</span><span class=identifier>Class</span><span class=special>::*</span><span class=identifier>PtrToMemberFunction</span><span class=special>)()></span> <span class=keyword>struct</span> <span class=identifier>mem_fun</span> <span class=special>{</span> <span class=keyword>typedef</span> <span class=keyword>typename</span> <span class=identifier>remove_reference</span><span class=special><</span><span class=identifier>Type</span><span class=special>>::</span><span class=identifier>type</span> <span class=identifier>result_type</span><span class=special>;</span> <span class=comment>// only provided if ChainedPtr& is not convertible to Class&</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>ChainedPtr</span><span class=special>></span> <span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>ChainedPtr</span><span class=special>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=identifier>Class</span><span class=special>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special><</span><span class=identifier>Class</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=special>};</span> </pre></blockquote> <p> The <code>PtrToMemberFunction</code> template argument specifies the particular <code>Type (Class::*PtrToMemberFunction)()</code> pointer to the the member function used in the extraction. <code>mem_fun<Class,Type,PtrToMemberFunction></code> is a model of: <ul> <li><a href="#key_extractors"><code>Key Extractor</code></a> from <code>reference_wrapper<Class></code>,</li> <li><a href="#key_extractors"><code>Key Extractor</code></a> from any <a href="#chained_pointers">chained pointer</a> to <code>Class</code>.</li> </ul> </p> <h4><code>mem_fun</code> members</h4> <code>template<typename ChainedPtr> Type operator()(const ChainedPtr& x)const;</code> <blockquote> <b>Requires:</b> <code>ChainedPtr</code> is a <a href="#chained_pointers">chained pointer</a> type to <code>Type</code>.<br> <b>Returns:</b> <code>(y.*PtrToMemberFunction)()</code>, where <code>y</code> is the object chained-pointed to by <code>x</code>. </blockquote> <code>Type operator()(Class& x)const;</code> <blockquote> <b>Returns:</b> <code>(x.*PtrToMemberFunction)()</code>. </blockquote> <code>Type operator()(const reference_wrapper<Class>& x)const;</code> <blockquote> <b>Returns:</b> <code>(x.get().*PtrToMemberFunction)()</code>. </blockquote> <h3><a name="const_mem_fun_explicit">Class template <code>const_mem_fun_explicit</code></a></h3> <p> MSVC++ 6.0 do not properly support pointers to constant member functions as non-type template parameters, thus <a href="#const_mem_fun"><code>const_mem_fun</code></a> cannot be used in this compiler. A simple workaround consists in specifying the <i>type</i> of these pointers as an additional template parameter. </p> <blockquote><pre> <span class=keyword>template</span><span class=special><</span> <span class=keyword>class</span> <span class=identifier>Class</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Type</span><span class=special>,</span> <span class=keyword>typename</span> <span class=identifier>PtrToMemberFunctionType</span><span class=special>,</span><span class=identifier>PtrToMemberFunctionType</span> <span class=identifier>PtrToMemberFunction</span> <span class=special>></span> <span class=keyword>struct</span> <span class=identifier>const_mem_fun_explicit</span> <span class=special>{</span> <span class=keyword>typedef</span> <span class=keyword>typename</span> <span class=identifier>remove_reference</span><span class=special><</span><span class=identifier>Type</span><span class=special>>::</span><span class=identifier>type</span> <span class=identifier>result_type</span><span class=special>;</span> <span class=comment>// only provided if const ChainedPtr& is not convertible to const Class&</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>ChainedPtr</span><span class=special>></span> <span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>ChainedPtr</span><span class=special>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>Class</span><span class=special>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special><</span><span class=keyword>const</span> <span class=identifier>Class</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special><</span><span class=identifier>Class</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=special>};</span> </pre></blockquote> <p> <code>const_mem_fun_explicit</code> provides the very same functionality as its <code>const_mem_fun</code> analogous instantiation. For example, given the type </p> <blockquote><pre> <span class=keyword>struct</span> <span class=identifier>A</span> <span class=special>{</span> <span class=keyword>int</span> <span class=identifier>f</span><span class=special>()</span><span class=keyword>const</span><span class=special>;</span> <span class=special>};</span> </pre></blockquote> <p> the extractor <code>const_mem_fun<A,int,&A::f></code> can be replaced by <code>const_mem_fun_explicit<A,int,int (A::*)()const,&A::f></code>. </p> <h3><a name="mem_fun_explicit">Class template <code>mem_fun_explicit</code></a></h3> <p> For analogy with <a href="#const_mem_fun_explicit"><code>const_mem_fun_explicit</code></a>, a variation of <a href="#mem_fun"><code>mem_fun</code></a> is provided accepting an additional parameter with the type of the pointer to non-constant member function used for extraction. </p> <blockquote><pre> <span class=keyword>template</span><span class=special><</span> <span class=keyword>class</span> <span class=identifier>Class</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Type</span><span class=special>,</span> <span class=keyword>typename</span> <span class=identifier>PtrToMemberFunctionType</span><span class=special>,</span><span class=identifier>PtrToMemberFunctionType</span> <span class=identifier>PtrToMemberFunction</span> <span class=special>></span> <span class=keyword>struct</span> <span class=identifier>mem_fun_explicit</span> <span class=special>{</span> <span class=keyword>typedef</span> <span class=keyword>typename</span> <span class=identifier>remove_reference</span><span class=special><</span><span class=identifier>Type</span><span class=special>>::</span><span class=identifier>type</span> <span class=identifier>result_type</span><span class=special>;</span> <span class=comment>// only provided if ChainedPtr& is not convertible to Class&</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>ChainedPtr</span><span class=special>></span> <span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>ChainedPtr</span><span class=special>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=identifier>Class</span><span class=special>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special><</span><span class=identifier>Class</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=special>};</span> </pre></blockquote> <h3><a name="boost_multi_index_const_mem_fun">Macro <code>BOOST_MULTI_INDEX_CONST_MEM_FUN</code></a></h3> <blockquote><pre> <span class=identifier>BOOST_MULTI_INDEX_CONST_MEM_FUN</span><span class=special>(</span><span class=identifier>Class</span><span class=special>,</span><span class=identifier>Type</span><span class=special>,</span><span class=identifier>MemberFunName</span><span class=special>)</span> </pre></blockquote> <p> Use this macro when writing cross-platform code selectively using <code>const_mem_fun_explicit</code> in place of <code>const_mem_fun</code> for compilers not supporting the latter. In the usual cases, the macro expands to </p> <blockquote><pre> <span class=special>::</span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>const_mem_fun</span><span class=special><</span><span class=identifier>Class</span><span class=special>,</span><span class=identifier>Type</span><span class=special>,&</span><span class=identifier>Class</span><span class=special>::</span><span class=identifier>MemberFunName</span><span class=special>></span> </pre></blockquote> <p> but it resolves to </p> <blockquote><pre> <span class=special>::</span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>const_mem_fun_explicit</span><span class=special><</span> <span class=identifier>Class</span><span class=special>,</span><span class=identifier>Type</span><span class=special>,</span><span class=identifier>Type</span> <span class=special>(</span><span class=identifier>Class</span><span class=special>::*)()</span><span class=keyword>const</span><span class=special>,&</span><span class=identifier>Class</span><span class=special>::</span><span class=identifier>MemberFunName</span> <span class=special>></span> </pre></blockquote> <p> for MSVC++ 6.0 or lower. </p> <h3><a name="boost_multi_index_mem_fun">Macro <code>BOOST_MULTI_INDEX_MEM_FUN</code></a></h3> <blockquote><pre> <span class=identifier>BOOST_MULTI_INDEX_MEM_FUN</span><span class=special>(</span><span class=identifier>Class</span><span class=special>,</span><span class=identifier>Type</span><span class=special>,</span><span class=identifier>MemberFunName</span><span class=special>)</span> </pre></blockquote> <p> By default, the macro expands to </p> <blockquote><pre> <span class=special>::</span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>mem_fun</span><span class=special><</span><span class=identifier>Class</span><span class=special>,</span><span class=identifier>Type</span><span class=special>,&</span><span class=identifier>Class</span><span class=special>::</span><span class=identifier>MemberFunName</span><span class=special>></span> </pre></blockquote> <p> but it resolves to </p> <blockquote><pre> <span class=special>::</span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>mem_fun_explicit</span><span class=special><</span> <span class=identifier>Class</span><span class=special>,</span><span class=identifier>Type</span><span class=special>,</span><span class=identifier>Type</span> <span class=special>(</span><span class=identifier>Class</span><span class=special>::*)()</span><span class=special>,&</span><span class=identifier>Class</span><span class=special>::</span><span class=identifier>MemberFunName</span> <span class=special>></span> </pre></blockquote> <p> for MSVC++ 6.0 or lower. </p> <h2> <a name="global_fun_synopsis">Header <a href="../../../../boost/multi_index/global_fun.hpp"> <code>"boost/multi_index/global_fun.hpp"</code></a> synopsis</a></h2> <blockquote><pre> <span class=keyword>namespace</span> <span class=identifier>boost</span><span class=special>{</span> <span class=keyword>namespace</span> <span class=identifier>multi_index</span><span class=special>{</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>class</span> <span class=identifier>Value</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Type</span><span class=special>,</span><span class=identifier>Type</span> <span class=special>(*</span><span class=identifier>PtrToFunction</span><span class=special>)(</span><span class=identifier>Value</span><span class=special>)></span> <span class=keyword>struct</span> <span class=identifier>global_fun</span><span class=special>;</span> <span class=special>}</span> <span class=comment>// namespace boost::multi_index</span> <span class=special>}</span> <span class=comment>// namespace boost</span> </pre></blockquote> <h3><a name="global_fun">Class template <code>global_fun</code></a></h3> <p> <code>global_fun</code> is a <a href="#key_extractors"><code>Key Extractor</code></a> based on a given global or static member function accepting the base type as argument and returning the associated key. </p> <blockquote><pre> <span class=keyword>template</span><span class=special><</span><span class=keyword>class</span> <span class=identifier>Value</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Type</span><span class=special>,</span><span class=identifier>Type</span> <span class=special>(*</span><span class=identifier>PtrToFunction</span><span class=special>)(</span><span class=identifier>Value</span><span class=special>)></span> <span class=keyword>struct</span> <span class=identifier>global_fun</span> <span class=special>{</span> <span class=keyword>typedef</span> <span class=keyword>typename</span> <span class=identifier>remove_reference</span><span class=special><</span><span class=identifier>Type</span><span class=special>>::</span><span class=identifier>type</span> <span class=identifier>result_type</span><span class=special>;</span> <span class=comment>// Only provided under the following circumstances: // - If Value is a reference to a constant type, only provided // when const ChainedPtr& is not convertible to Value; // - if Value is a reference to a non-const type, only provided // when ChainedPtr& is not convertible to Value; // - else, only provided when const ChainedPtr& is not // convertible to const Value&.</span> <span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>ChainedPtr</span><span class=special>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=comment>// only provided if Value is a reference type</span> <span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=identifier>Value</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=comment>// only provided if Value is not a reference type</span> <span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>Value</span><span class=special>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=comment>// only provided if Value is not a reference type</span> <span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special><</span><span class=keyword>const</span> <span class=identifier>Value</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=comment>// only provided if Value is a reference type</span> <span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span> <span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special><</span> <span class=identifier>remove_reference</span><span class=special><</span><span class=identifier>Value</span><span class=special>>::</span><span class=identifier>type</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=comment>// only provided if Value is not a reference type or is // a reference to a constant type</span> <span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span> <span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special><</span> <span class=keyword>typename</span> <span class=identifier>remove_const</span><span class=special><</span> <span class=keyword>typename</span> <span class=identifier>remove_reference</span><span class=special><</span><span class=identifier>Value</span><span class=special>>::</span><span class=identifier>type</span><span class=special>>::</span><span class=identifier>type</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=special>};</span> </pre></blockquote> <p> <code>PtrToFunction</code> specifies the particular function used to extract the key of type <code>Type</code> from some <code>BaseType</code>. <code>global_fun</code> supports the following function signatures: <ul> <li><code>Type f(BaseType)</code> (<code>Value</code> is <code>BaseType</code>),</li> <li><code>Type f(const BaseType&)</code> (<code>Value</code> is <code>const BaseType&</code>),</li> <li><code>Type f(BaseType&)</code> (<code>Value</code> is <code>BaseType&</code>).</li> </ul> <code>global_fun<Type,Value,PtrToFunction></code> is a model of: <ul> <li><a href="#key_extractors"><code>Key Extractor</code></a> from <code>reference_wrapper<BaseType></code>,</li> <li><a href="#key_extractors"><code>Key Extractor</code></a> from any <a href="#chained_pointers">chained pointer</a> to <code>BaseType</code>.</li> </ul> When <code>Value</code> is <code>BaseType</code> or <code>const BaseType&</code>, <code>global_fun<Type,Value,PtrToFunction></code> is also a model of: <ul> <li><a href="#key_extractors"><code>Key Extractor</code></a> from <code>BaseType</code>,</li> <li><a href="#key_extractors"><code>Key Extractor</code></a> from <code>reference_wrapper<const BaseType></code>,</li> <li><a href="#key_extractors"><code>Key Extractor</code></a> from any <a href="#chained_pointers">chained pointer</a> to <code>const BaseType</code>.</li> </ul> </p> <h4><code>global_fun</code> members</h4> <code>template<typename ChainedPtr> Type operator()(const ChainedPtr& x)const;</code> <blockquote> <b>Requires:</b> <code>ChainedPtr</code> is a <a href="#chained_pointers">chained pointer</a> type to <code>Value</code>.<br> <b>Returns:</b> <code>PtrToFunction)(y)</code>, where <code>y</code> is the object chained-pointed to by <code>x</code>. </blockquote> <code>Type operator()(Value x)const;</code> <blockquote> <b>Returns:</b> <code>PtrToFunction(x)</code>. </blockquote> <code>Type operator()(const Value& x)const;</code> <blockquote> <b>Returns:</b> <code>PtrToFunction(x)</code>. </blockquote> <code>Type operator()(const reference_wrapper<const Value>& x)const;</code> <blockquote> <b>Returns:</b> <code>PtrToFunction(x.get())</code>. </blockquote> <code> Type operator()(<br> const reference_wrapper<remove_reference<Value>::type>& x)const;</code> <blockquote> <b>Returns:</b> <code>PtrToFunction(x.get())</code>. </blockquote> <code>Type operator()(<br> const reference_wrapper<<br> typename remove_const<<br> typename remove_reference<Value>::type>::type>& x)const;</code> <blockquote> <b>Returns:</b> <code>PtrToFunction(x.get())</code>. </blockquote> <h2> <a name="composite_key_synopsis">Header <a href="../../../../boost/multi_index/composite_key.hpp"> <code>"boost/multi_index/composite_key.hpp"</code></a> synopsis</a></h2> <blockquote><pre> <span class=keyword>namespace</span> <span class=identifier>boost</span><span class=special>{</span> <span class=keyword>namespace</span> <span class=identifier>multi_index</span><span class=special>{</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>Value</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>KeyFromValue0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>KeyFromValuen</span><span class=special>></span> <span class=keyword>struct</span> <span class=identifier>composite_key</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>></span> <span class=keyword>struct</span> <span class=identifier>composite_key_result</span><span class=special>;</span> <span class=comment>// comparison operators for composite_key_result:</span> <span class=comment>// <b>OP</b> is any of ==,<,!=,>,>=,<=</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey1</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey2</span><span class=special>></span> <span class=keyword>bool</span> <span class=keyword>operator</span> <b><i>OP</i></b><span class=special>(</span> <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey1</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>,</span> <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey2</span><span class=special>>&</span> <span class=identifier>y</span><span class=special>);</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>></span> <span class=keyword>bool</span> <span class=keyword>operator</span> <b><i>OP</i></b><span class=special>(</span> <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>,</span> <span class=keyword>const</span> <span class=identifier>tuple</span><span class=special><</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>>&</span> <span class=identifier>y</span><span class=special>);</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>></span> <span class=keyword>bool</span> <span class=keyword>operator</span> <b><i>OP</i></b><span class=special>(</span> <span class=keyword>const</span> <span class=identifier>tuple</span><span class=special><</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>,</span> <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>y</span><span class=special>);</span> <span class=comment>// equality functors:</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>Pred0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Predn</span><span class=special>></span> <span class=keyword>struct</span> <span class=identifier>composite_key_equal_to</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKeyResult</span><span class=special>></span> <span class=keyword>struct</span> <span class=identifier>composite_key_result_equal_to</span><span class=special>;</span> <span class=comment>// comparison functors:</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>Compare0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Comparen</span><span class=special>></span> <span class=keyword>struct</span> <span class=identifier>composite_key_compare</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKeyResult</span><span class=special>></span> <span class=keyword>struct</span> <span class=identifier>composite_key_result_less</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKeyResult</span><span class=special>></span> <span class=keyword>struct</span> <span class=identifier>composite_key_result_greater</span><span class=special>;</span> <span class=comment>// hash functors:</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>Hash0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Hashn</span><span class=special>></span> <span class=keyword>struct</span> <span class=identifier>composite_key_hash</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKeyResult</span><span class=special>></span> <span class=keyword>struct</span> <span class=identifier>composite_key_result_hash</span><span class=special>;</span> <span class=special>}</span> <span class=comment>// namespace boost::multi_index</span> <span class=special>}</span> <span class=comment>// namespace boost</span> <span class=comment>// specializations of external functors for composite_key_result:</span> <span class=keyword>namespace</span> <span class=identifier>std</span><span class=special>{</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>></span> <span class=keyword>struct</span> <span class=identifier>equal_to</span><span class=special><</span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>></span> <span class=special>>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>></span> <span class=keyword>struct</span> <span class=identifier>less</span><span class=special><</span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>></span> <span class=special>>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>></span> <span class=keyword>struct</span> <span class=identifier>greater</span><span class=special><</span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>></span> <span class=special>>;</span> <span class=special>}</span> <span class=comment>// namespace std</span> <span class=keyword>namespace</span> <span class=identifier>boost</span><span class=special>{</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>></span> <span class=keyword>struct</span> <span class=identifier>hash</span><span class=special><</span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>></span> <span class=special>>;</span> <span class=special>}</span> <span class=comment>// namespace boost</span> </pre></blockquote> <h3><a name="composite_key">Class template <code>composite_key</code></a></h3> <p> <code>composite_key</code> is a <a href="#key_extractors"><code>Key Extractor</code></a> returning the combined value of several key extractors whose type is specified at compile time. The returned object is of type <a href="#composite_key_result"> <code>composite_key_result</code></a><code><composite_key></code>. </p> <blockquote><pre> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>Value</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>KeyFromValue0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>KeyFromValuen</span><span class=special>></span> <span class=keyword>struct</span> <span class=identifier>composite_key</span> <span class=special>{</span> <span class=keyword>typedef</span> <span class=identifier>tuple</span><span class=special><</span><span class=identifier>KeyFromValue0</span><span class=special>,...,</span><span class=identifier>KeyFromValuen</span><span class=special>></span> <span class=identifier>key_extractor_tuple</span><span class=special>;</span> <span class=keyword>typedef</span> <span class=identifier>Value</span> <span class=identifier>value_type</span><span class=special>;</span> <span class=keyword>typedef</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>composite_key</span><span class=special>></span> <span class=identifier>result_type</span><span class=special>;</span> <span class=identifier>composite_key</span><span class=special>(</span> <span class=keyword>const</span> <span class=identifier>KeyFromValue0</span><span class=special>&</span> <span class=identifier>k0</span><span class=special>=</span><span class=identifier>KeyFromValue0</span><span class=special>(),</span> <span class=special>...</span> <span class=keyword>const</span> <span class=identifier>KeyFromValuen</span><span class=special>&</span> <span class=identifier>kn</span><span class=special>=</span><span class=identifier>KeyFromValuen</span><span class=special>());</span> <span class=identifier>composite_key</span><span class=special>(</span><span class=keyword>const</span> <span class=identifier>key_extractor_tuple</span><span class=special>&</span> <span class=identifier>x</span><span class=special>);</span> <span class=keyword>const</span> <span class=identifier>key_extractor_tuple</span><span class=special>&</span> <span class=identifier>key_extractors</span><span class=special>()</span><span class=keyword>const</span><span class=special>;</span> <span class=identifier>key_extractor_tuple</span><span class=special>&</span> <span class=identifier>key_extractors</span><span class=special>()</span> <span class=comment>// only provided if const ChainedPtr& is not convertible to const value_type&</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>ChainedPtr</span><span class=special>></span> <span class=identifier>result_type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>ChainedPtr</span><span class=special>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=identifier>result_type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>value_type</span><span class=special>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=identifier>result_type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special><</span><span class=keyword>const</span> <span class=identifier>value_type</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=identifier>result_type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special><</span><span class=identifier>value_type</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=special>};</span> </pre></blockquote> <p> <code>KeyFromValue0</code>, ... , <code>KeyFromValuen</code> are the types of the key extractors combined into the composite key. Each of these types must be a <a href="#key_extractors"><code>Key Extractor</code></a> from <code>Value</code>. At least a key extractor must be provided. The maximum number of key extractors of a <code>composite_key</code> instantiation is implementation defined. <code>composite_key</code> internally stores an object of every constituent key extractor type. <code>composite_key<Value,KeyFromValue0,...,KeyFromValuen></code> is a model of: <ul> <li><a href="#key_extractors"><code>Key Extractor</code></a> from <code>Value</code>,</li> <li><a href="#key_extractors"><code>Key Extractor</code></a> from <code>reference_wrapper<const Value></code>,</li> <li><a href="#key_extractors"><code>Key Extractor</code></a> from <code>reference_wrapper<Value></code>,</li> <li><a href="#key_extractors"><code>Key Extractor</code></a> from any <a href="#chained_pointers">chained pointer</a> to <code>const Value</code>,</li> <li><a href="#key_extractors"><code>Key Extractor</code></a> from any <a href="#chained_pointers">chained pointer</a> to <code>Value</code>.</li> </ul> </p> <h4><code>composite_key</code> members</h4> <code>composite_key(<br> const KeyFromValue0& k0=KeyFromValue0(),<br> ...<br> const KeyFromValuen& kn=KeyFromValuen()); </code> <blockquote> <b>Effects:</b> Constructs a <code>composite_key</code> that stores copies of the key extractor objects supplied. </blockquote> <code>composite_key(const key_extractor_tuple& x);</code> <blockquote> <b>Effects:</b> Constructs a <code>composite_key</code> that stores copies of the key extractor objects supplied in <code>x</code>. </blockquote> <code>const key_extractor_tuple& key_extractors()const;</code> <blockquote> <b>Returns:</b> a constant reference to a tuple holding the key extractors internally stored by the <code>composite_key</code>. </blockquote> <code>key_extractor_tuple& key_extractors();</code> <blockquote> <b>Returns:</b> a reference to a tuple holding the key extractors internally stored by the <code>composite_key</code>. </blockquote> <code>template<typename ChainedPtr><br> result_type operator()(const ChainedPtr& x)const;</code> <blockquote> <b>Requires:</b> <code>ChainedPtr</code> is a <a href="#chained_pointers">chained pointer</a> type to <code>result_type</code>.<br> <b>Returns:</b> a <code>result_type</code> object dependent on <code>*this</code> and <code>y</code>, where <code>y</code> is the object chained-pointed to by <code>x</code>. </blockquote> <code>result_type operator()(const value_type& x)const;</code> <blockquote> <b>Returns:</b> a <code>result_type</code> object dependent on <code>*this</code> and <code>x</code>. </blockquote> <code>result_type operator()(const reference_wrapper<const value_type>& x)const;</code> <blockquote> <b>Returns:</b> a <code>result_type</code> object dependent on <code>*this</code> and <code>x.get()</code>. </blockquote> <code>result_type operator()(const reference_wrapper<value_type>& x)const;</code> <blockquote> <b>Returns:</b> a <code>result_type</code> object dependent on <code>*this</code> and <code>x.get()</code>. </blockquote> <h3><a name="composite_key_result">Class template <code>composite_key_result</code></a></h3> <p> This is an opaque type returned by <code>composite_key</code> instantiations as their extracted key. </p> <blockquote><pre> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>></span> <span class=keyword>struct</span> <span class=identifier>composite_key_result</span> <span class=special>{</span> <b>no public interface available</b> <span class=special>};</span> <span class=comment>// comparison:</span> <span class=comment>// <b>OP</b> is any of ==,<,!=,>,>=,<=</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey1</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey2</span><span class=special>></span> <span class=keyword>bool</span> <span class=keyword>operator</span> <b><i>OP</i></b><span class=special>(</span> <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey1</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>,</span> <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey2</span><span class=special>>&</span> <span class=identifier>y</span><span class=special>);</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>></span> <span class=keyword>bool</span> <span class=keyword>operator</span> <b><i>OP</i></b><span class=special>(</span> <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>,</span> <span class=keyword>const</span> <span class=identifier>tuple</span><span class=special><</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>>&</span> <span class=identifier>y</span><span class=special>);</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>></span> <span class=keyword>bool</span> <span class=keyword>operator</span> <b><i>OP</i></b><span class=special>(</span> <span class=keyword>const</span> <span class=identifier>tuple</span><span class=special><</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>,</span> <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>y</span><span class=special>);</span> </pre></blockquote> <code>CompositeKey</code> is the <code>composite_key</code> instantiation to which the <code>composite_key_result</code> type is associated. Objects of type <code>composite_key_result</code> returned by a composite key must be always treated as <i>temporary</i>, i.e. they should not be stored or copied. <code>composite_key_result</code> is <i>not</i> guaranteed to be a model of <a href="http://www.sgi.com/tech/stl/DefaultConstructible.html"> <code>Default Constructible</code></a> or <a href="http://www.sgi.com/tech/stl/Assignable.html"><code>Assignable</code></a>. Every object of type <code>composite_key_result<CompositeKey></code> is internally associated to the <code>CompositeKey</code> from which it is returned and the object of type <code>CompositeKey::value_type</code> to which the composite key was applied. </p> <h4><a name="ckey_result_notation">Notation</a></h4> <p> Given an <code>x</code> of type <code>composite_key_result<CompositeKey></code>, we use the following notation: <ul> <li><code>ck(x)</code> is the <code>CompositeKey</code> object associated to <code>x</code>,</li> <li><code>v(x)</code> is the object of type <code>CompositeKey::value_type</code> associated to <code>x</code>,</li> <li><code>k<sub>i</sub>(x) = ck(x).key_extractors().get<i>()</code>, that is, is the <code>i</code>-th key extractor of <code>ck(x)</code>,</li> <li><code>x<sub>i</sub> = k<sub>i</sub>(x)(v(x))</code>, that is, the key extracted from <code>v(x)</code> by the <code>i</code>-th key extractor,</li> <li><code>length(x)</code> is the number of key extractors of <code>ck(x)</code>.</li> </ul> Also, if <code>y</code> is a tuple of values, we define: <ul> <li><code>y<sub>i</sub>=y.get<i>()</code>,</li> <li><code>length(y)</code> is the number of elements of <code>y</code>.</li> </ul> </p> <h4>Comparison operators</h4> <code>template<typename CompositeKey1,typename CompositeKey2><br> bool operator==(<br> const composite_key_result<CompositeKey1>& x,<br> const composite_key_result<CompositeKey2>& y);<br> template<typename CompositeKey,typename Value0,...,typename Valuen><br> bool operator==(<br> const composite_key_result<CompositeKey>& x,<br> const tuple<Value0,...,Valuen>& y);<br> template<typename Value0,...,typename Valuen,typename CompositeKey><br> bool operator==(<br> const tuple<Value0,...,Valuen>& x,<br> const composite_key_result<CompositeKey>& y); </code> <blockquote> <b>Requires:</b> <code>length(x)==length(y)</code>. The expression <code>x<sub>i</sub>==y<sub>i</sub></code> is valid for all <code>i</code> in <code>[0,length(x))</code>.<br> <b>Returns:</b> <code>true</code> if and only if <blockquote> <code>x<sub>i</sub>==y<sub>i</sub></code> for all <code>i</code> in <code>[0,length(x))</code>. </blockquote> <b>Complexity:</b> No more key extraction operations and comparisons are performed than those necessary for the evaluation of the expression above, starting at <code>i==0</code>. The evaluation is short-circuited as soon as the result is determined to be <code>false</code>. </blockquote> <code>template<typename CompositeKey1,typename CompositeKey2><br> bool operator<(<br> const composite_key_result<CompositeKey1>& x,<br> const composite_key_result<CompositeKey2>& y);<br> template<typename CompositeKey,typename Value0,...,typename Valuen><br> bool operator<(<br> const composite_key_result<CompositeKey>& x,<br> const tuple<Value0,...,Valuen>& y);<br> template<typename Value0,...,typename Valuen,typename CompositeKey><br> bool operator<(<br> const tuple<Value0,...,Valuen>& x,<br> const composite_key_result<CompositeKey>& y); </code> <blockquote> <b>Requires:</b> The expressions <code>x<sub>i</sub><y<sub>i</sub></code> and <code>y<sub>i</sub><x<sub>i</sub></code> are valid for all <code>i</code> in <code>[0,min(length(x),length(y)))</code>.<br> <b>Returns:</b> <code>true</code> if and only if there exists some <code>j</code> in the range <code>[0,min(length(x),length(y)))</code> such that <blockquote> <code>!(x<sub>i</sub><y<sub>i</sub>) && !(y<sub>i</sub><x<sub>i</sub>)</code> for all <code>i</code> in <code>[0,j)</code>,<br> <code> x<sub>j</sub><y<sub>j</sub></code>. </blockquote> <b>Complexity:</b> No more key extraction operations and comparisons are performed than those necessary for the evaluation of the expression above, starting at <code>i==0</code>. The evaluation is short-circuited as soon as the result is determined to be <code>false</code>. </blockquote> <code>template<typename CompositeKey1,typename CompositeKey2><br> bool operator <b><i>OP</i></b>(<br> const composite_key_result<CompositeKey1>& x,<br> const composite_key_result<CompositeKey2>& y);<br> template<typename CompositeKey,typename Value0,...,typename Valuen><br> bool operator <b><i>OP</i></b>(<br> const composite_key_result<CompositeKey>& x,<br> const tuple<Value0,...,Valuen>& y);<br> template<typename Value0,...,typename Valuen,typename CompositeKey><br> bool operator <b><i>OP</i></b>(<br> const tuple<Value0,...,Valuen>& x,<br> const composite_key_result<CompositeKey>& y); </code> <p> (<code><b><i>OP</i></b></code> is any of <code>!=</code>, <code>></code>, <code>>=</code>, <code><=</code>.) </p> <blockquote> <b>Requires:</b> The expressions given below are valid (for the particular <code><b><i>OP</i></b></code> considered.)<br> <b>Returns:</b> <code>true</code> if and only if <blockquote> <code>!(x==y)</code> (<code><b><i>OP</i></b></code> is <code>!=</code>),<br> <code> y< x </code> (<code><b><i>OP</i></b></code> is <code>> </code>),<br> <code>!(x< y)</code> (<code><b><i>OP</i></b></code> is <code>>=</code>),<br> <code>!(y< x)</code> (<code><b><i>OP</i></b></code> is <code><=</code>). </blockquote> </blockquote> <h3><a name="ckey_result_equality">Equality</a></h3> <h4><a name="composite_key_equal_to">Class template <code>composite_key_equal_to</code></a></h4> <p> <code>composite_key_equal_to</code> tests for equality between <code>composite_key_result</code> instantiations and between these and tuples of values, using an internally stored collection of elementary equality predicates. </p> <blockquote><pre> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>Pred0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Predn</span><span class=special>></span> <span class=keyword>struct</span> <span class=identifier>composite_key_equal_to</span> <span class=special>{</span> <span class=keyword>typedef</span> <span class=identifier>tuple</span><span class=special><</span><span class=identifier>Pred0</span><span class=special>,...,</span><span class=identifier>Predn</span><span class=special>></span> <span class=identifier>key_eq_tuple</span><span class=special>;</span> <span class=identifier>composite_key_equal_to</span><span class=special>(</span> <span class=keyword>const</span> <span class=identifier>Pred0</span><span class=special>&</span> <span class=identifier>p0</span><span class=special>=</span><span class=identifier>Pred0</span><span class=special>(),</span> <span class=special>...</span> <span class=keyword>const</span> <span class=identifier>Predn</span><span class=special>&</span> <span class=identifier>pn</span><span class=special>=</span><span class=identifier>Predn</span><span class=special>());</span> <span class=identifier>composite_key_equal_to</span><span class=special>(</span><span class=keyword>const</span> <span class=identifier>key_eq_tuple</span><span class=special>&</span> <span class=identifier>x</span><span class=special>);</span> <span class=keyword>const</span> <span class=identifier>key_eq_tuple</span><span class=special>&</span> <span class=identifier>key_eqs</span><span class=special>()</span><span class=keyword>const</span><span class=special>;</span> <span class=identifier>key_eq_tuple</span><span class=special>&</span> <span class=identifier>key_eqs</span><span class=special>()</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey1</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey2</span><span class=special>></span> <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span> <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey1</span><span class=special>></span> <span class=special>&</span> <span class=identifier>x</span><span class=special>,</span> <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey2</span><span class=special>></span> <span class=special>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>></span> <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span> <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>,</span> <span class=keyword>const</span> <span class=identifier>tuple</span><span class=special><</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>></span> <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span> <span class=keyword>const</span> <span class=identifier>tuple</span><span class=special><</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>,</span> <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=special>};</span> </pre></blockquote> <p> <code>Pred0</code>, ... , <code>Predn</code> are the types of the equality predicates stored by <code>composite_key_equal_to</code>. Each of these types must be a <a href="http://www.sgi.com/tech/stl/BinaryPredicate.html"> <code>Binary Predicate</code></a>. At least an equality predicate must be provided. The maximum number of equality predicates of a <code>composite_key_equal_to</code> instantiation is implementation defined. <code>composite_key_equal_to</code> is <a href="http://www.sgi.com/tech/stl/Assignable.html"><code>Assignable</code></a>. It is also <a href="http://www.sgi.com/tech/stl/DefaultConstructible.html"> <code>Default Constructible</code></a> if each <code>Predi</code> is <a href="http://www.sgi.com/tech/stl/DefaultConstructible.html"> <code>Default Constructible</code></a>. </p> <p> Note that formally it is not required that the <code>Predi</code> types behave as equality predicates in any definite way. However, the semantics of <code>composite_key_equal_to</code> is well defined if this is the case, as explained in the section on the <a href="#ckey_result_semantics">semantics of <code>composite_key_result</code></a>. </p> <h4>Notation</h4> <p> In what follows we use the same <a href="#ckey_result_notation">notation</a> introduced for <code>composite_key_result</code>. <h4><code>composite_key_equal_to</code> members</h4> <code>composite_key_equal_to(<br> const Pred0& p0=Pred0(),<br> ...<br> const Predn& pn=Predn()); </code> <blockquote> <b>Effects:</b> Constructs a <code>composite_key_equal_to</code> that stores copies of the equality predicates supplied. </blockquote> <code>composite_key_equal_to(const key_eq_tuple& x);</code> <blockquote> <b>Effects:</b> Constructs a <code>composite_key_equal_to</code> that stores copies of the equality predicate objects supplied in <code>x</code>. </blockquote> <code>const key_eq_tuple& key_eqs()const;</code> <blockquote> <b>Returns:</b> a constant reference to a tuple holding the equality predicate objects internally stored by the <code>composite_key_equal_to</code>. </blockquote> <code>key_eq_tuple& key_eqs();</code> <blockquote> <b>Returns:</b> a reference to a tuple holding the equality predicate objects internally stored by the <code>composite_key_equal_to</code>. </blockquote> <code> template<typename CompositeKey1,typename CompositeKey2><br> bool operator()(<br> const composite_key_result<CompositeKey1> & x,<br> const composite_key_result<CompositeKey2> & y)const;<br> template<typename CompositeKey,typename Value0,...,typename Valuen><br> bool operator()(<br> const composite_key_result<CompositeKey>& x,<br> const tuple<Value0,...,Valuen>& y)const;<br> template<typename Value0,...,typename Valuen,typename CompositeKey><br> bool operator()(<br> const tuple<Value0,...,Valuen>& x,<br> const composite_key_result<CompositeKey>& y)const;<br> </code> <blockquote> <b>Requires:</b> <code>length(x)==length(y)</code>. The expressions <code>key_eqs().get<i>()(x<sub>i</sub>,y<sub>i</sub>)</code> and <code>key_eqs().get<i>()(y<sub>i</sub>,x<sub>i</sub>)</code> are valid for all <code>i</code> in <code>[0,length(x))</code>.<br> <b>Returns:</b> <code>true</code> if and only <blockquote> <code>key_eqs().get<i>()(x<sub>i</sub>,y<sub>i</sub>)</code> for all <code>i</code> in <code>[0,length(x))</code>.<br> </blockquote> <b>Complexity:</b> No more key extraction operations and comparisons are performed than those necessary for the evaluation of the expression above, starting at <code>i==0</code>. The evaluation is short-circuited as soon as the result is determined to be <code>false</code>. </blockquote> <h4><a name="composite_key_result_equal_to">Class template <code>composite_key_result_equal_to</code></a></h4> <p> <code>composite_key_result_equal_to</code> acts as a particularization of <code>composite_key_equal_to</code> where all the comparison predicates supplied are instantiations of <code>std::equal_to</code>. </p> <blockquote><pre> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKeyResult</span><span class=special>></span> <span class=keyword>struct</span> <span class=identifier>composite_key_result_equal_to</span> <span class=special>{</span> <span class=keyword>typedef</span> <span class=identifier>CompositeKeyResult</span> <span class=identifier>first_argument_type</span><span class=special>;</span> <span class=keyword>typedef</span> <span class=identifier>first_argument_type</span> <span class=identifier>second_argument_type</span><span class=special>;</span> <span class=keyword>typedef</span> <span class=keyword>bool</span> <span class=identifier>result_type</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey1</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey2</span><span class=special>></span> <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span> <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey1</span><span class=special>></span> <span class=special>&</span> <span class=identifier>x</span><span class=special>,</span> <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey2</span><span class=special>></span> <span class=special>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>></span> <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span> <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>,</span> <span class=keyword>const</span> <span class=identifier>tuple</span><span class=special><</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>></span> <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span> <span class=keyword>const</span> <span class=identifier>tuple</span><span class=special><</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>,</span> <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=special>};</span> </pre></blockquote> <p> <code>CompositeKeyResult</code> must be an instantiation of <code>composite_key_result</code> for some type <code>composite_key<KeyFromValue0,...,KeyFromValuen></code>. <code>composite_key_result_equal_to<CompositeKeyResult>::operator()</code> is then equivalent to <code>composite_key_equal_to<Pred0,...,Predn>::operator()</code>, taking <blockquote> <code>Predi = std::equal_to<KeyFromValuei::result_type></code> for all <code>i = 0,...,n</code>. </blockquote> </p> <p> In addition to the requirements on <code>Predi</code> imposed by <code>composite_key_equal_to</code>, each of these types must be <a href="http://www.sgi.com/tech/stl/DefaultConstructible.html"> <code>Default Constructible</code></a>. <code>composite_key_result_equal_to</code> is <a href="http://www.sgi.com/tech/stl/DefaultConstructible.html"> <code>Default Constructible</code></a> and <a href="http://www.sgi.com/tech/stl/Assignable.html"><code>Assignable</code></a>. </p> <h4><a name="equal_to_composite_key_result">Specialization of <code>std::equal_to</code> for <code>composite_key</code> results</a></h4> <p> <code>std::equal_to<CompositeKeyResult></code>, for <code>CompositeKeyResult</code> being an instantiation of <code>composite_key_result</code>, has the same interface and functionality as <code>composite_key_result_equal_to<CompositeKeyResult></code>. </p> <blockquote><pre> <span class=keyword>namespace</span> <span class=identifier>std</span><span class=special>{</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>></span> <span class=keyword>struct</span> <span class=identifier>equal_to</span><span class=special><</span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>></span> <span class=special>></span> <span class=special>{</span> <span class=keyword>typedef</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special><</span> <span class=identifier>CompositeKey</span><span class=special>></span> <span class=identifier>first_argument_type</span><span class=special>;</span> <span class=keyword>typedef</span> <span class=identifier>first_argument_type</span> <span class=identifier>second_argument_type</span><span class=special>;</span> <span class=keyword>typedef</span> <span class=keyword>bool</span> <span class=identifier>result_type</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey1</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey2</span><span class=special>></span> <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span> <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey1</span><span class=special>></span> <span class=special>&</span> <span class=identifier>x</span><span class=special>,</span> <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey2</span><span class=special>></span> <span class=special>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>></span> <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span> <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>,</span> <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>tuple</span><span class=special><</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>></span> <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span> <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>tuple</span><span class=special><</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>,</span> <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=special>};</span> <span class=special>}</span> <span class=comment>// namespace std</span> </pre></blockquote> <h3><a name="ckey_result_comparison">Comparison</a></h3> <h4><a name="composite_key_compare">Class template <code>composite_key_compare</code></a></h4> <p> <code>composite_key_compare</code> compares <code>composite_key_result</code> instantiations between them and with tuples of values using an internally stored collection of elementary comparison predicates. </p> <blockquote><pre> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>Compare0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Comparen</span><span class=special>></span> <span class=keyword>struct</span> <span class=identifier>composite_key_compare</span> <span class=special>{</span> <span class=keyword>typedef</span> <span class=identifier>tuple</span><span class=special><</span><span class=identifier>Compare0</span><span class=special>,...,</span><span class=identifier>Comparen</span><span class=special>></span> <span class=identifier>key_comp_tuple</span><span class=special>;</span> <span class=identifier>composite_key_compare</span><span class=special>(</span> <span class=keyword>const</span> <span class=identifier>Compare0</span><span class=special>&</span> <span class=identifier>c0</span><span class=special>=</span><span class=identifier>Compare0</span><span class=special>(),</span> <span class=special>...</span> <span class=keyword>const</span> <span class=identifier>Comparen</span><span class=special>&</span> <span class=identifier>cn</span><span class=special>=</span><span class=identifier>Comparen</span><span class=special>());</span> <span class=identifier>composite_key_compare</span><span class=special>(</span><span class=keyword>const</span> <span class=identifier>key_comp_tuple</span><span class=special>&</span> <span class=identifier>x</span><span class=special>);</span> <span class=keyword>const</span> <span class=identifier>key_comp_tuple</span><span class=special>&</span> <span class=identifier>key_comps</span><span class=special>()</span><span class=keyword>const</span><span class=special>;</span> <span class=identifier>key_comp_tuple</span><span class=special>&</span> <span class=identifier>key_comps</span><span class=special>()</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey1</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey2</span><span class=special>></span> <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span> <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey1</span><span class=special>></span> <span class=special>&</span> <span class=identifier>x</span><span class=special>,</span> <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey2</span><span class=special>></span> <span class=special>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>></span> <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span> <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>,</span> <span class=keyword>const</span> <span class=identifier>tuple</span><span class=special><</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>></span> <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span> <span class=keyword>const</span> <span class=identifier>tuple</span><span class=special><</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>,</span> <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Value</span><span class=special>></span> <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span> <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>,</span><span class=keyword>const</span> <span class=identifier>Value</span><span class=special>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>Value</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>></span> <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span> <span class=keyword>const</span> <span class=identifier>Value</span><span class=special>&</span> <span class=identifier>x</span><span class=special>,</span><span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=special>};</span> </pre></blockquote> <p> <code>Compare0</code>, ... , <code>Comparen</code> are the types of the comparison predicates stored by <code>composite_key_compare</code>. Each of these types must be a <a href="http://www.sgi.com/tech/stl/BinaryPredicate.html"> <code>Binary Predicate</code></a>. At least a comparison predicate must be provided. The maximum number of comparison predicates of a <code>composite_key_compare</code> instantiation is implementation defined. <code>composite_key_compare</code> is <a href="http://www.sgi.com/tech/stl/Assignable.html"><code>Assignable</code></a>. It is also <a href="http://www.sgi.com/tech/stl/DefaultConstructible.html"> <code>Default Constructible</code></a> if each <code>Comparei</code> is <a href="http://www.sgi.com/tech/stl/DefaultConstructible.html"> <code>Default Constructible</code></a>. </p> <p> Note that formally it is not required that the <code>Comparei</code> types behave as comparison predicates in any definite way. However, the semantics of <code>composite_key_compare</code> is well defined if this is the case, as explained in the section on the <a href="#ckey_result_semantics">semantics of <code>composite_key_result</code></a>. </p> <h4>Notation</h4> <p> In what follows we use the same <a href="#ckey_result_notation">notation</a> introduced for <code>composite_key_result</code>. <h4><code>composite_key_compare</code> members</h4> <code>composite_key_compare(<br> const Compare0& c0=Compare0(),<br> ...<br> const Comparen& cn=Comparen()); </code> <blockquote> <b>Effects:</b> Constructs a <code>composite_key_compare</code> that stores copies of the comparison predicates supplied. </blockquote> <code>composite_key_compare(const key_comp_tuple& x);</code> <blockquote> <b>Effects:</b> Constructs a <code>composite_key_compare</code> that stores copies of the comparison predicate objects supplied in <code>x</code>. </blockquote> <code>const key_comp_tuple& key_comps()const;</code> <blockquote> <b>Returns:</b> a constant reference to a tuple holding the comparison predicate objects internally stored by the <code>composite_key_compare</code>. </blockquote> <code>key_comp_tuple& key_comps();</code> <blockquote> <b>Returns:</b> a reference to a tuple holding the comparison predicate objects internally stored by the <code>composite_key_compare</code>. </blockquote> <code> template<typename CompositeKey1,typename CompositeKey2><br> bool operator()(<br> const composite_key_result<CompositeKey1> & x,<br> const composite_key_result<CompositeKey2> & y)const;<br> template<typename CompositeKey,typename Value0,...,typename Valuen><br> bool operator()(<br> const composite_key_result<CompositeKey>& x,<br> const tuple<Value0,...,Valuen>& y)const;<br> template<typename Value0,...,typename Valuen,typename CompositeKey><br> bool operator()(<br> const tuple<Value0,...,Valuen>& x,<br> const composite_key_result<CompositeKey>& y)const;<br> </code> <blockquote> <b>Requires:</b> The expressions <code>key_comps().get<i>()(x<sub>i</sub>,y<sub>i</sub>)</code> and <code>key_comps().get<i>()(y<sub>i</sub>,x<sub>i</sub>)</code> are valid for all <code>i</code> in <code>[0,min(length(x),length(y)))</code>.<br> <b>Returns:</b> <code>true</code> if and only if there exists some <code>j</code> in the range <code>[0,min(length(x),length(y)))</code> such that <blockquote> <code>!key_comps().get<i>()(x<sub>i</sub>,y<sub>i</sub>) && !key_comps().get<i>()(y<sub>i</sub>,x<sub>i</sub>)</code> for all <code>i</code> in <code>[0,j)</code>,<br> <code> key_comps().get<j>()(x<sub>j</sub>,y<sub>j</sub>)</code>. </blockquote> <b>Complexity:</b> No more key extraction operations and comparisons are performed than those necessary for the evaluation of the expression above, starting at <code>i==0</code>. The evaluation is short-circuited as soon as the result is determined to be <code>false</code>. </blockquote> <code> template<typename CompositeKey,typename Value><br> bool operator()(<br> const composite_key_result<CompositeKey>& x,const Value& y)const; </code> <blockquote> <b>Effects:</b> <blockquote><pre> <span class=keyword>return</span> <span class=keyword>operator</span><span class=special>()(</span><span class=identifier>x</span><span class=special>,</span><span class=identifier>make_tuple</span><span class=special>(</span><span class=identifier>cref</span><span class=special>(</span><span class=identifier>y</span><span class=special>)));</span> </pre></blockquote><br> </blockquote> <code> template<typename Value,typename CompositeKey><br> bool operator()(<br> const Value& x,const composite_key_result<CompositeKey>& y)const; </code> <blockquote> <b>Effects:</b> <blockquote><pre> <span class=keyword>return</span> <span class=keyword>operator</span><span class=special>()(</span><span class=identifier>make_tuple</span><span class=special>(</span><span class=identifier>cref</span><span class=special>(</span><span class=identifier>x</span><span class=special>)),</span><span class=identifier>y</span><span class=special>);</span> </pre></blockquote><br> </blockquote> <h4><a name="composite_key_result_less">Class template <code>composite_key_result_less</code></a></h4> <p> <code>composite_key_result_less</code> acts as a particularization of <code>composite_key_compare</code> where all the comparison predicates supplied are instantiations of <code>std::less</code>. </p> <blockquote><pre> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKeyResult</span><span class=special>></span> <span class=keyword>struct</span> <span class=identifier>composite_key_result_less</span> <span class=special>{</span> <span class=keyword>typedef</span> <span class=identifier>CompositeKeyResult</span> <span class=identifier>first_argument_type</span><span class=special>;</span> <span class=keyword>typedef</span> <span class=identifier>first_argument_type</span> <span class=identifier>second_argument_type</span><span class=special>;</span> <span class=keyword>typedef</span> <span class=keyword>bool</span> <span class=identifier>result_type</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey1</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey2</span><span class=special>></span> <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span> <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey1</span><span class=special>></span> <span class=special>&</span> <span class=identifier>x</span><span class=special>,</span> <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey2</span><span class=special>></span> <span class=special>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>></span> <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span> <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>,</span> <span class=keyword>const</span> <span class=identifier>tuple</span><span class=special><</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>></span> <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span> <span class=keyword>const</span> <span class=identifier>tuple</span><span class=special><</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>,</span> <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Value</span><span class=special>></span> <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span> <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>,</span><span class=keyword>const</span> <span class=identifier>Value</span><span class=special>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>Value</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>></span> <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span> <span class=keyword>const</span> <span class=identifier>Value</span><span class=special>&</span> <span class=identifier>x</span><span class=special>,</span><span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=special>};</span> </pre></blockquote> <p> <code>CompositeKeyResult</code> must be an instantiation of <code>composite_key_result</code> for some type <code>composite_key<KeyFromValue0,...,KeyFromValuen></code>. <code>composite_key_result_less<CompositeKeyResult>::operator()</code> is then equivalent to <code>composite_key_compare<Compare0,...,Comparen>::operator()</code>, taking <blockquote> <code>Comparei = std::less<KeyFromValuei::result_type></code> for all <code>i = 0,...,n</code>. </blockquote> </p> <p> In addition to the requirements on <code>Comparei</code> imposed by <code>composite_key_compare</code>, each of these types must be <a href="http://www.sgi.com/tech/stl/DefaultConstructible.html"> <code>Default Constructible</code></a>. <code>composite_key_result_less</code> is <a href="http://www.sgi.com/tech/stl/DefaultConstructible.html"> <code>Default Constructible</code></a> and <a href="http://www.sgi.com/tech/stl/Assignable.html"><code>Assignable</code></a>. </p> <h4><a name="composite_key_result_greater">Class template <code>composite_key_result_greater</code></a></h4> <p> <code>composite_key_result</code> acts as a particularization of <code>composite_key_compare</code> where all the comparison predicates supplied are instantiations of <code>std::greater</code>. </p> <blockquote><pre> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKeyResult</span><span class=special>></span> <span class=keyword>struct</span> <span class=identifier>composite_key_result_greater</span> <span class=special>{</span> <span class=keyword>typedef</span> <span class=identifier>CompositeKeyResult</span> <span class=identifier>first_argument_type</span><span class=special>;</span> <span class=keyword>typedef</span> <span class=identifier>first_argument_type</span> <span class=identifier>second_argument_type</span><span class=special>;</span> <span class=keyword>typedef</span> <span class=keyword>bool</span> <span class=identifier>result_type</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey1</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey2</span><span class=special>></span> <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span> <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey1</span><span class=special>></span> <span class=special>&</span> <span class=identifier>x</span><span class=special>,</span> <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey2</span><span class=special>></span> <span class=special>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>></span> <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span> <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>,</span> <span class=keyword>const</span> <span class=identifier>tuple</span><span class=special><</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>></span> <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span> <span class=keyword>const</span> <span class=identifier>tuple</span><span class=special><</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>,</span> <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Value</span><span class=special>></span> <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span> <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>,</span><span class=keyword>const</span> <span class=identifier>Value</span><span class=special>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>Value</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>></span> <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span> <span class=keyword>const</span> <span class=identifier>Value</span><span class=special>&</span> <span class=identifier>x</span><span class=special>,</span><span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=special>};</span> </pre></blockquote> <p> <code>CompositeKeyResult</code> must be an instantiation of <code>composite_key_result</code> for some type <code>composite_key<KeyFromValue0,...,KeyFromValuen></code>. <code>composite_key_result_greater<CompositeKeyResult>::operator()</code> is then equivalent to <code>composite_key_compare<Compare0,...,Comparen>::operator()</code>, taking <blockquote> <code>Comparei = std::greater<KeyFromValuei::result_type></code> for all <code>i = 0,...,n</code>. </blockquote> </p> <p> In addition to the requirements on <code>Comparei</code> imposed by <code>composite_key_compare</code>, each of these types must be <a href="http://www.sgi.com/tech/stl/DefaultConstructible.html"> <code>Default Constructible</code></a>. <code>composite_key_result_greater</code> is <a href="http://www.sgi.com/tech/stl/DefaultConstructible.html"> <code>Default Constructible</code></a> and <a href="http://www.sgi.com/tech/stl/Assignable.html"><code>Assignable</code></a>. </p> <h4><a name="less_composite_key_result">Specialization of <code>std::less</code> for <code>composite_key</code> results</a></h4> <p> <code>std::less<CompositeKeyResult></code>, for <code>CompositeKeyResult</code> being an instantiation of <code>composite_key_result</code>, has the same interface and functionality as <code>composite_key_result_less<CompositeKeyResult></code>. </p> <blockquote><pre> <span class=keyword>namespace</span> <span class=identifier>std</span><span class=special>{</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>></span> <span class=keyword>struct</span> <span class=identifier>less</span><span class=special><</span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>></span> <span class=special>></span> <span class=special>{</span> <span class=keyword>typedef</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special><</span> <span class=identifier>CompositeKey</span><span class=special>></span> <span class=identifier>first_argument_type</span><span class=special>;</span> <span class=keyword>typedef</span> <span class=identifier>first_argument_type</span> <span class=identifier>second_argument_type</span><span class=special>;</span> <span class=keyword>typedef</span> <span class=keyword>bool</span> <span class=identifier>result_type</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey1</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey2</span><span class=special>></span> <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span> <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey1</span><span class=special>></span> <span class=special>&</span> <span class=identifier>x</span><span class=special>,</span> <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey2</span><span class=special>></span> <span class=special>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>></span> <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span> <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>,</span> <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>tuple</span><span class=special><</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>></span> <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span> <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>tuple</span><span class=special><</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>,</span> <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Value</span><span class=special>></span> <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span> <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>,</span> <span class=keyword>const</span> <span class=identifier>Value</span><span class=special>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>Value</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>></span> <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span> <span class=keyword>const</span> <span class=identifier>Value</span><span class=special>&</span> <span class=identifier>x</span><span class=special>,</span> <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=special>};</span> <span class=special>}</span> <span class=comment>// namespace std</span> </pre></blockquote> <h4><a name="greater_composite_key_result">Specialization of <code>std::greater</code> for <code>composite_key</code> results</a></h4> <p> <code>std::greater<CompositeKeyResult></code>, for <code>CompositeKeyResult</code> being an instantiation of <code>composite_key_result</code>, has the same interface and functionality as <code>composite_key_result_greater<CompositeKeyResult></code>. </p> <blockquote><pre> <span class=keyword>namespace</span> <span class=identifier>std</span><span class=special>{</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>></span> <span class=keyword>struct</span> <span class=identifier>greater</span><span class=special><</span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>></span> <span class=special>></span> <span class=special>{</span> <span class=keyword>typedef</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special><</span> <span class=identifier>CompositeKey</span><span class=special>></span> <span class=identifier>first_argument_type</span><span class=special>;</span> <span class=keyword>typedef</span> <span class=identifier>first_argument_type</span> <span class=identifier>second_argument_type</span><span class=special>;</span> <span class=keyword>typedef</span> <span class=keyword>bool</span> <span class=identifier>result_type</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey1</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey2</span><span class=special>></span> <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span> <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey1</span><span class=special>></span> <span class=special>&</span> <span class=identifier>x</span><span class=special>,</span> <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey2</span><span class=special>></span> <span class=special>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>></span> <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span> <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>,</span> <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>tuple</span><span class=special><</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>></span> <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span> <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>tuple</span><span class=special><</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>,</span> <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Value</span><span class=special>></span> <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span> <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>,</span> <span class=keyword>const</span> <span class=identifier>Value</span><span class=special>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>Value</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>></span> <span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span> <span class=keyword>const</span> <span class=identifier>Value</span><span class=special>&</span> <span class=identifier>x</span><span class=special>,</span> <span class=keyword>const</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=special>};</span> <span class=special>}</span> <span class=comment>// namespace std</span> </pre></blockquote> <h3><a name="ckey_result_hashing">Hashing</a></h3> <h4><a name="composite_key_hash">Class template <code>composite_key_hash</code></a></h4> <p> <code>composite_key_hash</code> produces hash values for <code>composite_key_result</code> instantiations based on a collection of elementary hash functors. </p> <blockquote><pre> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>Hash0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Hashn</span><span class=special>></span> <span class=keyword>struct</span> <span class=identifier>composite_key_hash</span> <span class=special>{</span> <span class=keyword>typedef</span> <span class=identifier>tuple</span><span class=special><</span><span class=identifier>Hash0</span><span class=special>,...,</span><span class=identifier>Hashn</span><span class=special>></span> <span class=identifier>key_hasher_tuple</span><span class=special>;</span> <span class=identifier>composite_key_hash</span><span class=special>(</span> <span class=keyword>const</span> <span class=identifier>Hash0</span><span class=special>&</span> <span class=identifier>h0</span><span class=special>=</span><span class=identifier>Hash0</span><span class=special>(),</span> <span class=special>...</span> <span class=keyword>const</span> <span class=identifier>Hashn</span><span class=special>&</span> <span class=identifier>hn</span><span class=special>=</span><span class=identifier>Hashn</span><span class=special>());</span> <span class=identifier>composite_key_hash</span><span class=special>(</span><span class=keyword>const</span> <span class=identifier>key_hasher_tuple</span><span class=special>&</span> <span class=identifier>x</span><span class=special>);</span> <span class=keyword>const</span> <span class=identifier>key_hasher_tuple</span><span class=special>&</span> <span class=identifier>key_hash_functions</span><span class=special>()</span><span class=keyword>const</span><span class=special>;</span> <span class=identifier>key_hasher_tuple</span><span class=special>&</span> <span class=identifier>key_hash_functions</span><span class=special>()</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>></span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>size_t</span> <span class=keyword>operator</span><span class=special>()(</span> <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>></span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>size_t</span> <span class=keyword>operator</span><span class=special>()(</span> <span class=keyword>const</span> <span class=identifier>tuple</span><span class=special><</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=special>};</span> </pre></blockquote> <p> <code>Hash0</code>, ... , <code>Hashn</code> are the types of the hash functors stored by <code>composite_key_hash</code>. Each of these types must be a <a href="http://www.sgi.com/tech/stl/UnaryFunction.html"><code>Unary Function</code></a> returning a value of type <code>std::size_t</code> in the range <code>[0, std::numeric_limits<std::size_t>::max())</code>. At least a hash functor must be provided. The maximum number of hash functors of a <code>composite_key_hash</code> instantiation is implementation defined. <code>composite_key_hash</code> is <a href="http://www.sgi.com/tech/stl/Assignable.html"><code>Assignable</code></a>. It is also <a href="http://www.sgi.com/tech/stl/DefaultConstructible.html"> <code>Default Constructible</code></a> if each <code>Hashi</code> is <a href="http://www.sgi.com/tech/stl/DefaultConstructible.html"> <code>Default Constructible</code></a>. </p> <h4>Notation</h4> <p> In what follows we use the same <a href="#ckey_result_notation">notation</a> introduced for <code>composite_key_result</code>. <h4><code>composite_key_hash</code> members</h4> <code>composite_key_hash(<br> const Hash0& h0=Hash0(),<br> ...<br> const Hashn& hn=Hashn()); </code> <blockquote> <b>Effects:</b> Constructs a <code>composite_key_hash</code> that stores copies of the hash functors supplied. </blockquote> <code>composite_key_hash(const key_hasher_tuple& x);</code> <blockquote> <b>Effects:</b> Constructs a <code>composite_key_hash</code> that stores copies of the hash functors supplied in <code>x</code>. </blockquote> <code>const key_hasher_tuple& key_hash_functions()const;</code> <blockquote> <b>Returns:</b> a constant reference to a tuple holding the hash functors internally stored by the <code>composite_key_hash</code>. </blockquote> <code>key_hasher_tuple& key_hash_functions();</code> <blockquote> <b>Returns:</b> a reference to a tuple holding the hash functors internally stored by the <code>composite_key_hash</code>. </blockquote> <code> template<typename CompositeKey><br> bool operator()(<br> const composite_key_result<CompositeKey>& x)const;<br> template<typename Value0,...,typename Valuen><br> bool operator()(<br> const tuple<Value0,...,Valuen>& x)const; </code> <blockquote> <b>Requires:</b> <code>length(x)==length(key_hash_functions())</code>. The expression <code>key_hash_functions().get<i>()(x<sub>i</sub>)</code> is valid for all <code>i</code> in <code>[0,length(x))</code>. <br> <b>Returns:</b> A value in the range <code>[0, std::numeric_limits<std::size_t>::max())</code> that solely depends on the numerical tuple <blockquote> (<code>key_hash_functions().get<0>()(x<sub>0</sub>)</code>, ... , <code>key_hash_functions().get<N>()(x<sub>N</sub>)</code>), with <code>N=length(x)-1</code>. </blockquote> </blockquote> <h4><a name="composite_key_result_hash">Class template <code>composite_key_result_hash</code></a></h4> <p> <code>composite_key_result_hash</code> acts as a particularization of <code>composite_key_hash</code> where all the hash functors supplied are instantiations of <a href="../../../functional/hash/index.html"><code>boost::hash</code></a>. </p> <blockquote><pre> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKeyResult</span><span class=special>></span> <span class=keyword>struct</span> <span class=identifier>composite_key_result_hash</span> <span class=special>{</span> <span class=keyword>typedef</span> <span class=identifier>CompositeKeyResult</span> <span class=identifier>argument_type</span><span class=special>;</span> <span class=keyword>typedef</span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>size_t</span> <span class=identifier>result_type</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>></span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>size_t</span> <span class=keyword>operator</span><span class=special>()(</span> <span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>></span><span class=special>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>></span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>size_t</span> <span class=keyword>operator</span><span class=special>()(</span> <span class=keyword>const</span> <span class=identifier>tuple</span><span class=special><</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=special>};</span> </pre></blockquote> <p> <code>CompositeKeyResult</code> must be an instantiation of <code>composite_key_result</code> for some type <code>composite_key<KeyFromValue0,...,KeyFromValuen></code>. <code>composite_key_result_hash<CompositeKeyResult>::operator()</code> is then equivalent to <code>composite_key_hash<Hash0,...,Hashn>::operator()</code>, taking <blockquote> <code>Hashi = boost::hash<KeyFromValuei::result_type></code> for all <code>i = 0,...,n</code>. </blockquote> </p> <p> In addition to the requirements on <code>Hashi</code> imposed by <code>composite_key_hash</code>, each of these types must be <a href="http://www.sgi.com/tech/stl/DefaultConstructible.html"> <code>Default Constructible</code></a>. <code>composite_key_result_hash</code> is <a href="http://www.sgi.com/tech/stl/DefaultConstructible.html"> <code>Default Constructible</code></a> and <a href="http://www.sgi.com/tech/stl/Assignable.html"><code>Assignable</code></a>. </p> <h4><a name="hash_composite_key_result">Specialization of <a href="../../../functional/hash/index.html"><code>boost::hash</code></a> for <code>composite_key</code> results</a></h4> <p> <code>boost::hash<CompositeKeyResult></code>, for <code>CompositeKeyResult</code> being an instantiation of <code>composite_key_result</code>, has the same interface and functionality as <code>composite_key_result_hash<CompositeKeyResult></code>. </p> <blockquote><pre> <span class=keyword>namespace</span> <span class=identifier>boost</span><span class=special>{</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>></span> <span class=keyword>struct</span> <span class=identifier>hash</span><span class=special><</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>></span> <span class=special>></span> <span class=special>{</span> <span class=keyword>typedef</span> <span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>></span> <span class=identifier>argument_type</span><span class=special>;</span> <span class=keyword>typedef</span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>size_t</span> <span class=identifier>result_type</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>></span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>size_t</span> <span class=keyword>operator</span><span class=special>()(</span> <span class=keyword>const</span> <span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>></span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>size_t</span> <span class=keyword>operator</span><span class=special>()(</span> <span class=keyword>const</span> <span class=identifier>tuple</span><span class=special><</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=special>};</span> <span class=special>}</span> <span class=comment>// namespace boost</span> </pre></blockquote> <h3><a name="ckey_result_semantics">Semantics of <code>composite_key_result</code></a></h3> <p> The design of equality, comparison and hash operations for <code>composite_key_result</code> objects is based on the following rationale: a <code>composite_key_result</code> is regarded as a "virtual" tuple, each of its elements being the result of the corresponding elementary key extractor. Accordingly, any given operation resolves to a combination of the corresponding elementwise operations. This mapping preserves the fundamental properties of the elementary operations involved; for instance, it defines a true equivalence relation if the basic predicates induce equivalence relations themselves. We can state these facts in a formal way as follows. </p> <p> Consider an instantiation of <code>composite_key_equal_to</code> with types <code>Pred0</code>, ... , <code>Predn</code> such that each <code>Predi</code> induces an equivalence relation on a certain type <code>Ti</code>, and let <code>CompositeKey</code> be a type of the form <code>composite_key<Value,KeyFromValue0,...,KeyFromValuej></code>, with <code>j <= n</code>, such that <blockquote> <code>KeyFromValuei::result_type = Ti</code>, for all <code>i = 0,...,j</code>. </blockquote> Then, <code>composite_key_equal_to</code> induces an equivalence relation on elements of type <code>composite_key_result<CompositeKey></code>; such two objects are equivalent if all its elementary key extractor values are also equivalent. Additionally, given an instantiation <code>composite_key_hash<Hash0,...,Hashj></code>, the following types are <a href="hash_indices.html#lookup"><code>Compatible Keys</code></a> of (<code>composite_key_hash</code>, <code>composite_key_equal_to</code>) with respect to <code>composite_key_result<CompositeKey></code>: <blockquote> <code>tuple<Q0,...,Qj></code>,<br> <code>composite_key_result<composite_key<K0,...,Kj> ></code>, with <code>Ki::result_type = Qi</code> for all <code>i = 0,...,j</code>. </blockquote> provided that each <code>Qi</code> is either <code>Ti</code> or a <a href="hash_indices.html#lookup"><code>Compatible Key</code></a> of (<code>Hashi</code>, <code>Predi</code>).</p> <p> As for comparison, consider an instantiation of <code>composite_key_compare</code> with types <code>Compare0</code>, ... , <code>Comparen</code> such that each <code>Comparei</code> is a <a href="http://www.sgi.com/tech/stl/StrictWeakOrdering.html"><code>Strict Weak Ordering</code></a> on the type <code>Ti</code>. Then, for a <code>CompositeKey</code> type defined in the same manner as above, <code>composite_key_compare</code> is a <a href="http://www.sgi.com/tech/stl/StrictWeakOrdering.html"><code>Strict Weak Ordering</code></a> on elements of type <code>composite_key_result<CompositeKey></code>, and the order induced is lexicographical. Also, the following types are <a href="ord_indices.html#set_operations"><code>Compatible Keys</code></a> of <code>composite_key_compare</code> with respect to <code>composite_key_result<CompositeKey></code>: <blockquote> <code>tuple<Q0,...,Qk></code>, <code>k <= n</code><br> <code>composite_key_result<composite_key<K0,...,Kk> ></code>, with <code>Ki::result_type = Qi</code> for all <code>i = 0,...,k</code>. </blockquote> provided that <ul> <li>for <code>i = 0,...,min(j,k)-1</code>, <code>Qi</code> is either <code>Ti</code> or <i>not coarser</i> than <code>Ti</code> (<code>Qi</code> is a <a href="ord_indices.html#set_operations"><code>Compatible Key</code></a> of <code>Comparei</code> and there are no two distinct elements of <code>Ti</code> equivalent to one single element of <code>Qi</code>); </li> <li> <code>Qm</code> (with <code>m = min(j,k)</code>) is either <code>Tm</code> or a <a href="ord_indices.html#set_operations"><code>Compatible Key</code></a> of <code>Comparem</code>. </li> </ul> In this case, the comparison is done lexicographically only on the first <code>1+min(j,k)</code> elements. </p> <p> Analogous properties hold for the equality and comparison operators of <code>composite_key_result</code>. Note, however, that equality is only defined for objects of the same length, whilst comparison takes the minimum length of the operands considered. Therefore, the equivalence classes induced by <code>x==y</code> are subsets of those associated to <code>!(x<y)&&!(y<x)</code>. </p> <hr> <div class="prev_link"><a href="rnd_indices.html"><img src="../prev.gif" alt="random access indices" border="0"><br> Random access indices </a></div> <div class="up_link"><a href="index.html"><img src="../up.gif" alt="Boost.MultiIndex reference" border="0"><br> Boost.MultiIndex reference </a></div> <div class="next_link"><a href="../compiler_specifics.html"><img src="../next.gif" alt="compiler specifics" border="0"><br> Compiler specifics </a></div><br clear="all" style="clear: all;"> <br> <p>Revised June 25th 2008</p> <p>© Copyright 2003-2008 Joaquín M López Muñoz. Distributed under the Boost Software License, Version 1.0. (See accompanying file <a href="../../../../LICENSE_1_0.txt"> LICENSE_1_0.txt</a> or copy at <a href="http://www.boost.org/LICENSE_1_0.txt"> http://www.boost.org/LICENSE_1_0.txt</a>) </p> </body> </html>